---
name: "libressl-BIO_printf"
section: "3"
platform: "linux"
package: "libressl"
version: "4.4.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/libressl-BIO_printf"
---

# libressl-BIO\_printf(3)

formatted output to a BIO

## NAME

**BIO\_printf** – formatted output to a BIO

## SYNOPSIS

Crypto Library (libcrypto, -lcrypto)

**#include \<openssl/bio.h\>**

*int*\

**BIO\_printf**(*BIO \*bio*, *const char \*format*, *...*);

## DESCRIPTION

**BIO\_printf**() is a wrapper around [vfprintf(3)](/vfprintf/3.md), sending the output to the specified *bio*.

## RETURN VALUES

These functions return the number of bytes written, or -1 if an error occurs.

## SEE ALSO

BIO\_new(3)

## HISTORY

**BIO\_printf**() first appeared in SSLeay 0.6.5 and has been available since OpenBSD 2.4.